This invention relates to a plasma arc torch which is used in metalworking processes including plasma arc cutting, plasma arc welding and other metal surface treatments. More specifically, the present invention relates to a plasma arc torch disconnect and visible indicia means for early warning and safe operation of the torch.
Plasma arc torches operate by the electrical heating of a plasma-forming gas, i.e., nitrogen, compressed air, argon and hydrogen, for example, issuing from an arc constricting orifice in a torch tip. The plasma gas becomes an arc which issues from the torch tip for a variety of metalworking operations. For a complete description of the principals of operation of typical plasma arc torches including operating data, process applications, typical equipment, gases and other components, reference is made to the article entitled "Plasma Arc Metalworking Processes" written by Robert L. O'Brien, published by The American Welding Society in April 1967. This article provides a complete background and working understanding of plasma arc metalworking processes.
Plasma arc torches have many advantages over other competitive processes and are used in an ever increasing variety of metalworking applications. Because of this, many improvements have been made in the torches themselves and the way in which they operate. One area of concern is where there is a breakdown in the plasma arc process. In most cases, the breakdown is torch related since the other elements of the plasma arc metalworking system are not active working components in the operation, as is the case with plasma arc torches. As can be appreciated, torches are exposed to very high temperatures and high electric currents that are generated by the plasma arc metalworking process. Thus, the great majority of problems occur in the torch itself. When a torch fails to operate, substantial production down time occurs, and the high labor cost involved in such a breakdown encourages early warning and detection of an anticipated breakdown. Operator safety is also critical because of the high temperatures and currents involved in this process.